
Creating a RAID set
Some applications, such as video processing, require fast access to large amounts of information on disk. Other applications, such as those that track bank transactions, need to ensure that information isn't lost and the system continues to operate if a disk fails.
Using several hard disks, you can create a RAID (Redundant Array of Independent Disks) set to optimize performance and increase reliability in case of a disk failure.
To create a RAID set, you must use two or more SCSI or IDE hard disks. When you create a set, you specify the type of RAID set that corresponds to the requirements of the applications you will use with it:
- Mirrored RAID Set duplicates files on each disk in the set so that, if one of the disks fails, you have a continuous back up of the information. You may also be able to continue processing transactions.
- Striped RAID Set stores files in segments ("stripes") across all the disks in the set. Stripping improves the performance of applications that use large amounts of data.
You can also use several disks or volumes to create a "concatenated" set to use the disks in the set as if they are one disk. Although a concatenated set is not a true RAID type, you can use concatenated disk sets with a RAID set.
If you booted your computer from disk that has multiple partitions, you cannot create a RAID set that contains partitions from your boot disk. To create a RAID disk that contains partitions from that disk, you must boot your computer from another disk first.
- In Disk Utility, select one of the disks in the list that you want to use in the set and click RAID.
- Type a name for the RAID set and choose a format from the Volume Format pop-up menu.
- Choose a RAID type from the pop-up menu.
- Drag the disks you want to use in the set to the list on the right.
If you are creating a mirrored RAID set, you can choose a type for each disk from the RAID Type pop-up menu. Choose "slice" to make the disk a regular member of the set, choose "spare" to have the RAID set only start using the disk if one of the other disks fails.
- Click the Options button to specify an optimal block size for the data stored on the set. If you are creating a mirrored RAID set, select RAID Mirror AutoRebuild. Click OK when you're finished.
- Click Create.
After you create a RAID set, the RAID software manages storing files on the disks in the set for you.
If you have sufficient disks, you can create more than one RAID set. For example, you can set up one set as a mirrored RAID set to provide data redundancy, and another set as a striped RAID set to provide faster performance.